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This work presents an extensive review of hierarchical control strategies that provide effective and robust control for a DC microgrid. DC microgrid is an efficient, scalable and reliable solution for electrification in remote areas and needs a reliable control scheme such as hierarchical control. The hierarchical control strategy is divided into three layers namely primary, secondary and tertiary based on their functionality. In this study, different methods of primary control for current and voltage regulation, secondary control for error-correction in voltage and current, power sharing in a microgrid and microgrid clusters and tertiary control for power and energy management with a primary focus on minimal power loss and operational cost in a DC microgrid system are reviewed in-depth. Along with this, the advantages and limitations of various control structures like centralised, decentralised, distributed are discussed in this study. After a comparative study of all control strategies, the optimum control schemes from the author's point of view are also presented.

In this work, a modified generalised integrator with DC offset elimination capability is presented herein for the control of a unified power quality conditioner (UPQC) with solar photovoltaic array (SPVA) (UPQC-SPVA) system. Using this method, the fundamental element of load current is extracted, which is processed to generate reference currents for shunt active filter of the UPQC-SPVA system. This control algorithm improves power quality (PQ) such as grid currents balancing, harmonics elimination, compensation of reactive power, grid voltage sag and voltage swell mitigation. This system gives clean energy benefits along with PQ improvement by an integration of solar PV array at the DC link of UPQC. Simulation results are depicted to evaluate the performance of the UPQC in MATLAB/Simulink environment under presence of local non-linear load. The performance of UPQC-SPVA system is evaluated experimentally on a prototype in the laboratory and test results are found satisfactory for various disturbances like grid voltage sag/swell, load unbalancing, harmonics compensation and solar irradiation variation. The total harmonic distortion of the grid current is attained within limits of the IEEE-519 and IEEE-1159 standards.

This paper presents a comprehensive review on renewable energy based electric vehicle charging techniques, energy storage system with grid support functionality. The classification of electric vehicles charging based on standards, and charging techniques have been reviewed. Based on efficiency, feasibility and reliability, renewable energy like solar PV for electric vehicle charging are addressed. The energy storage system must be properly managed and safely maintained to improve the overall efficiency of electric vehicles for service longevity. A qualitative analysis of power electronics topologies along with its advantages and disadvantages are also discussed. Furthermore, a comprehensive analysis of Vehicle-Grid-Integration (VGI) infrastructure its capability, benefits/potential, challenges such as technological, environmental, economic etc. have also been highlighted. A comparative overview of power electronics topologies suitable for electric vehicle charging with VGI infrastructure is also exhibited.

In this paper, a modified generalized integrator (GI) control technique with a reduced number of integrators, is presented for the control of grid interfaced single stage solar PV array integrating with unified power quality conditioner (SPVA-UPQC) system. This controller has a reduced number of integrators to estimate the fundamental active components of the distorted signals enabling DC offset elimination. Further, these fundamental signals are used to generate the reference signals for shunt compensator. The SPVA-UPQC helps to mitigate both current and voltage related power quality (PQ) problems such as it eliminates harmonics, load unbalancing, reactive power compensation, voltage sag-swell elimination, as well as it provides clean energy generation, by interfacing solar PV array at the common DC link of UPQC. In order to evaluate the performance of this system with presence of nonlinear load, simulation results are presented in environment of MATLAB/Simulink. The experimental performance of the SPVA-UPQC system is validated through developed prototype and the corresponding results are presented herein for various conditions like grid voltage sag, grid voltage swell, load unbalancing, solar irradiation variation and harmonics. The total harmonic distortion (THD) of the grid voltages and currents are attained within the limits as per the IEEE-519 and IEEE-1159 standards.

In this work, a novel technique based on adaptive filtering is proposed for the control of a three-phase universal active power filter with a solar photovoltaic array integrated into its dc bus. Two adaptive filters along with a zero crossing detection technique are used to extract the magnitude of a fundamental active component of distorted load currents, which is then used in estimation of a reference signal for the shunt active filter. This technique enables extraction of an active component of all three phases with reduced mathematical computation. The series active filter control is based on synchronous reference frame theory and it regulates load voltage and maintains it in-phase with voltage at point of common coupling under conditions of voltage sag and swell. The performance of the system is evaluated on an experimental prototype in the laboratory under various dynamic conditions such as sag and swell in voltage at point of common coupling, load unbalancing, and change in solar irradiation intensity.

This study proposes a control approach based on second-order generalised integrator (SOGI) and delayed signal cancellation (DSC) for improved control of single-phase two-stage solar photovoltaic array integrated unified power quality conditioner (UPQC-SPV). The SPV array is integrated to the DC link of UPQC-SPV through a simple boost converter. The boost converter is controlled using a maximum power point tracking algorithm to operate SPV array at its peak power point. The series compensator control is based on extraction of point of common coupling voltage template using two cascaded SOGI (CSOGI) band-pass filter. The shunt compensator control is based on extraction on fundamental load current. As the load current is highly non-linear, a combination of CSOGI and DSC is used to extract fundamental active component of load current, from which the reference signal for shunt compensator is generated. This approach allows good accuracy in extraction of fundamental component of load current without sacrificing the dynamic performance. The performance of UPQC-SPV is verified experimentally on a prototype developed in the laboratory under dynamic conditions such as load change, voltage sags/swells and irradiation variation.

This paper proposes a modified pq-theory-based control of a solar photovoltaic (PV)-array-integrated unified power quality conditioner (PV-UPQC-S). The system incorporates clean energy generation along with power quality improvement, thus increasing functionality of the system. The fundamental-frequency positive-sequence components of voltages at the point of common coupling (PCC) are extracted using the generalized cascaded delay signal cancellation technique, which are then used in pq-theory-based control to estimate reference signals for the PV-UPQC-S. This modification in pq theory enables its application for PV-UPQC-S control under conditions of distorted PCC voltages. The series voltage-source converter (VSC) of the PV-UPQC-S operates such that it shares a part of the reactive power of the load even under nominal grid conditions. This increases the utilization of the series VSC while reducing the rating of shunt VSC. The PV array is integrated at the dc bus of the UPQC and provides a part of active load power, thus reducing demand on the supply system. The dynamic performance of the modified pq-theory-based PV-UPQC-S is verified by simulating the system in MATLAB-Simulink with a combination of linear and nonlinear loads. The steady-state and dynamic performances of the system are then experimentally validated through extensive testing on a scaled-down laboratory prototype.

In this work, a novel control of single-phase solar photovoltaic (PV) fed unified active power filter (PV-UAPF) is proposed for use in low-voltage distribution system. The shunt voltage source converter (VSC) of PV-UAPF mitigates current power quality issues such as current harmonics, reactive current etc. while the series VSC of PV-UAPF protects the sensitive load against point of common coupling (PCC) voltage disturbances. The shunt VSC control is based on extraction of fundamental load active current using recursive least squares with a variable forgetting factor. The proposed method improves the dynamic response of the system without sacrificing the steady-state performance. The series VSC is controlled using a proportional-resonant controller and it injects voltage in/out phase with PCC voltage during voltage sags/swells, respectively. The PV array which is integrated at the DC link of the PV-UAPF through a reverse blocking diode, provides the load power demand and also supplies remaining power into PCC. The system performance is evaluated using Matlab-Simulink software and is then experimentally verified on a prototype developed in the laboratory under steady-state and dynamic conditions such as irradiation variation, PCC voltage fluctuations and load disturbances to validate the performance of the system.

This work presents the performance of solar PV-battery integrated universal active power filter (PV-B-UAPF) in both grid connected and islanded modes of operation. The system consists of a right shunt universal active power filter in which the PV array is linked at the DC-bus of the system. The battery is connected to the DC-link through a bi-directional converter. The BES enables operation of the system in islanded mode. The system is evaluated using Matlab-Simulink software. The system behavior is evaluated under both grid connected and standalone modes of operation along with transition between both the modes. The performance is further evaluated under PCC voltage sags/swells, irradiation variation and load removal conditions.

This work proposes a novel control technique for the control of universal active power filter with distribution generation capabilities (UAPF-DG). The proposed technique uses a complex filter to estimate the per phase active component of load current in a three phase system. The methodology uses complex filter to obtain fundamental balanced positive sequence component of distorted load current. This is used in reference generation of shunt active filter of UAPF-DG. This technique is inherently a three phase technique and involves lower computational burden The UAPF-DG system regulates the voltage of sensitive loads while simultaneously compensating the nonlinear load currents, thus achieving unity power at point of common coupling (PCC). The performance of the proposed system is validated on an experimental setup and tested for its response under conditions of load unbalance, voltage rise/dip and variation in solar irradiation.

A discrete second order generalized integrator (DSOGI) based control is presented in this work for control of solar photovoltaic integrated unified power quality conditioner (SPV-UPQC). Two DSOGI based band-pass filters are used to extract fundamental positive sequence component (FPSC) of unbalanced grid voltages. The shunt compensator of SPV-UPQC is controlled based on philosophy of drawing balanced positive sequence currents (BPSC) from the point of common coupling (PCC). The shunt compensator has the dual function of compensating for load power quality issues along with injecting power from solar photovoltaic (SPV) array. Sensitive loads are protected against grid voltage fluctuations such as voltage sags/swells etc with the help of the series compensator of SPV-UPQC. A step-up DC-DC converter is used for coupling SPV array to the DC-bus of SPV-UPQC. A Maximum power point tracking (MPPT) algorithm generates appropriate duty cycle for the dc-dc converter so that the SPV array is operated at its peak power. The performance of DSOGI based SPV-UPQC is simulated in Matlab-Simulink environment and tested under dynamic conditions of grid voltage disturbances, load disturbances and solar irradiation variation.

A novel and computationally efficient method for d-q control of solar photovoltaic (SPV) integrated UPQC (PV-UPQC) is presented in this paper. A digital filter is used to extract fundamental positive sequence (FPS) component of distorted grid voltage which is used to generate the sine and cosine values necessary in d-q based control. The shunt compensator of PV-UPQC compensates for the load side power quality issues along with injecting active power from SPV array. The SPV array is integrated to the DC-bus of the PV-UPQC through a step up DC-DC converter. The step up converter is controlled by maximum power point tracking (MPPT) algorithm which extracts peak power available from the PV array. The control of series compensator of PV-UPQC which compensates for grid side power quality issues is such that the voltage is injected in-phase with grid voltage. The algorithm is implemented in a three-phase four-wire UPQC consisting of three leg series compensator and four leg shunt compensator. The system is simulated in Matlab-Simulink environment using a combination of nonlinear current fed load and a single phase linear load. The dynamic performance of the system is analyzed under conditions of grid voltage sag/swell, irradiation variation and load disturbances.

In this paper, a digital adaptive notch filter (DANF) based control algorithm is presented for a solar photovoltaic integrated unified power quality conditioner (PV-UPQC). Two DANFs are used for extraction of fundamental active current amplitude and also fundamental grid voltage template. The PV array is integrated directly to the DC-link of PV-UPQC. The shunt compensator compensates for the load current harmonics and also supplies active power from PV array into the grid while maintaining DC-link voltage. The series compensator of PV-UPQC compensates for grid voltage sags and swells. The PV-UPQC system is modeled and its performance is simulated in Matlab-Simulink under dynamic conditions such as irradiation variation and grid voltage sag/swell.

This paper deals with the design and performance analysis of a three-phase single stage solar photovoltaic integrated unified power quality conditioner (PV-UPQC). The PV-UPQC consists of a shunt and series-connected voltage compensators connected back-to-back with common dc-link. The shunt compensator performs the dual function of extracting power from PV array apart from compensating for load current harmonics. An improved synchronous reference frame control based on moving average filter is used for extraction of load active current component for improved performance of the PV-UPQC. The series compensator compensates for the grid side power quality problems such as grid voltage sags/swells. The compensator injects voltage in-phase/out of phase with point of common coupling (PCC) voltage during sag and swell conditions, respectively. The proposed system combines both the benefits of clean energy generation along with improving power quality. The steady state and dynamic performance of the system are evaluated by simulating in MATLAB-Simulink under a nonlinear load. The system performance is then verified using a scaled down laboratory prototype under a number of disturbances such as load unbalancing, PCC voltage sags/swells, and irradiation variation.